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A-level Biology Longridge Towers School > Chapter 5 Cell Recognition and the Immune System > Flashcards

Chapter 5 Cell Recognition and the Immune System Flashcards

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1
Q

What is a pathogen?

A

A microorganism which causes disease.

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2
Q

What is immunity?

A

The body’s ability to kill a pathogen before it causes any harm.

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3
Q

What are the 2 types of white blood cells?

A

Lymphocyte and phagocyte

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4
Q

What are the two types of lymphocytes?

A

T-Lymphocyte and B-Lymphocyte.

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5
Q

Why must white blood cells be able to distinguish between cell and non-self?

A

This allows the white blood cells to know what is part of your body, and what is not. So that the body’s own tissues aren’t destroyed.

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6
Q

What is used to identify cells as self or non-self?

A

The proteins on the cell surface membrane.

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7
Q

Why are proteins used to identify whether cells are self or non-self?

A

They have a huge variability and the 3-D (tertiary) structure is very specific.

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8
Q

What is the immune system able to identify?

A

1 - Pathogens (e.g. HIV); 2 - Non-self material (e.g. cells from another organism); 3 - Toxins; 4 - Abnormal body cells (e.g. cancer)

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9
Q

What is the name given to the protein which causes an immune response?

A

An antigen.

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10
Q

What issue may arise with the immune system, due to transplants?

A

The immune system may recognise the tissues as non-self, and therefore attack transplanted organs/tissues.

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11
Q

What are the 2 types of defence?

A

Specific and non-specific.

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12
Q

What are the 2 types of non-specific defence?

A

Physical barrier and phagocytosis.

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13
Q

What are the 2 types of specific defence?

A

Cell mediated response and humoral response.

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14
Q

What type of cells are involved in cell-mediated response?

A

T Lymphocytes.

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15
Q

What type of cells are involved in humoral response?

A

B Lymphocytes

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16
Q

When a pathogen enters the body, how is the correct lymphocyte selected?

A

It already exists in the body, but must be stimulated to replicate.

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17
Q

What do we mean by “correct” lymphocyte for a particular pathogen?

A

Just as each pathogen has specific proteins on their surface that indicate what they are. The lymphocytes have complementary proteins which fit those of the pathogen.

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18
Q

Why do lymphocytes not attack our own body?

A

1 - As a foetus, our lymphocytes were only exposed to our own cells, those which combined, were destroyed, leaving only those which fit foreign (non-self) material.
2 - As an adult, lymphocytes are created in the bone marrow, and again only encounter self antigens. if an immune response is triggered, the cell kills itself (apoptosis). Therefore no anti-self lymphocytes reach the blood.

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19
Q

What is the role of a phagocyte?

A

To ingest and destroy pathogens. (phagocytosis)

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20
Q

What is phagocytosis?

A

The ingesting of large particles into vesicles by the cell-surface membrane.

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21
Q

Describe phagocytosis

A

The pathogen releases chemicals.
This attracts the phagocyte.
The phagocyte binds to the pathogen.
The phagocyte engulfs the pathogen and forms a phagosome around the pathogen.
Lysosomes inside the phagocyte fuse with the phagosome to form a phagolysosome and release digestive enzymes into the phagosome.
The pathogen is broken down by hydrolysis.
The phagocyte presents antigens on its cell surface membrane.

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22
Q

What attracts phagocytes?

A

chemical products of pathogens, or dead, damaged or abnormal cells.

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23
Q

What allows phagocytes to recognise and attach to chemicals on the surface of the pathogen?

A

Receptors on the cell-surface membrane.

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24
Q

When the pathogen is engulfed, what is the vesicle called?

A

A phagosome.

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25
Q

What fuses with the phagosome?

A

Lysosomes.

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26
Q

What do the lysosomes contain and what do they do to the pathogen?

A

The lysosomes contain hydrolytic enzymes called lysozymes. These break down the pathogen. Similar to digestion.

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27
Q

What happens after the pathogen has been digested in the phagosome?

A

The soluble products are absorbed into the cytoplasm of the phagocyte.

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28
Q

What is cell mediated immunity?

A

The response of T-Lymphocytes to foreign antigens presented on a body cell.

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29
Q

What is an antigen?

A

Part of an organism or substance which is recognised as non-self and stimulates an immune response.

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30
Q

What form do most antigens take?

A

Proteins on the cell surface membrane.

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31
Q

Which white blood cell is involved in the specific immune response?

A

Lymphocytes

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32
Q

Where are the two types of Lymphocytes made and matured?

A

T-Lymphocytes are made in the bone marrow, and matured in the Thymus gland. B-Lymphocytes are made and matured in the Bone marrow.

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33
Q

What role do B-Lymphocytes play in the immune system?

A

They are associated with humoral immunity. (antibodies in the body’s fluids, or humor, such as plasma.)

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34
Q

What role do T-Lymphocytes play in the immune system?

A

They are associated with the cell mediated immunity. Immunity involving body cells.

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35
Q

What do T-Lymphocytes respond to?

A

The body’s own cells which have been infected. Cells from individuals of the same species (genetically different).

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36
Q

Why can T-Lymphocytes identify invader cells from normal cells?

A

Phagocytes present antigens of hydrolyzed pathogens on their surface membrane.
Body cells present viral antigens on their surface during infection.
Transplanted cells have different antigens on their surface.
Cancer cells are different, so present different antigens on their surface membrane.

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37
Q

What is an antigen presenting cell?

A

A cell which presents antigens which are foreign on their cell surface membrane.

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38
Q

Which antigens will T-Lymphocytes respond to?

A

Foreign antigens presented on a body cell. (cell-mediated immunity).

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39
Q

Why are there a vast number of different T-Cells?

A

Each T-Cell’s receptors correspond to one specific antigen. There needs to be many different T-Cells to correspond to the variation in antigens.

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40
Q

What are the stages of T-Cell response to infection by a pathogen?

A

1 - Phagocyte ingests pathogen;
2 - Pathogen’s antigens are placed onto the phagocyte’s surface membrane. (It becomes an APC)
3 - The receptors of a specific TH cell bind perfectly to the antigen being presented.
4 - This binding activates the Th cell to divide and produce many clones. (Clonal expansion)
5 - These cloned cells specialise.

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41
Q

In what way might cloned TH cells differentiate?

A

1 - Develop into memory cells
2 - Stimulate phagocytes
3 - Stimulate B-cells to divide and secrete antibodies
4 - Activate TC cells (Cytotoxic cells.)

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42
Q

What chemicals do cytotoxic (TC Cells) produce?

A

Perforin

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43
Q

How does perforin kill pathogens?

A

It perforates (makes little holes) in the membrane. This makes it freely permeable, so it dies.

44
Q

What pathogens do TC cells work best against? Why?

A

Viruses. Viruses only replicate when in a host cell. If the host cell dies, replication can no longer occur.

45
Q

What is meant by humoral immunity?

A

The second stage of an immune response, causing B cells to produce antibodies which dissolve into the blood and tissue fluid (the humour)

46
Q

Why are there many million types of B cell?

A

Each one creates an antibody to respond to a specific antigen. The variations in antigens require a large number of different antibodies.

47
Q

What does a B cell have on its surface to fit the invasive antigen?

A

A specific antibody. This antibody will only fit this antigen and vice versa.

48
Q

What does a B Cell do to the antigen when it has attached to the antibody on its surface?

A

It is taken in by endocytosis and the presented on the surface (It is an APC)

49
Q

How is a B-Cell stimulated to divide by mitosis?

A

An activated TH cell binds to the processed antigens on the B cell to stimulate it to divide by mitosis, creating clones. This is clonal selection.

50
Q

Why are more than 1 type of B-Cell activated for each pathogen?

A

Each pathogen typically has many proteins on its surface membrane, acting as antigens. They also produce toxins. All of these can stimulate B-Cells to make clones.

51
Q

What are the antibodies created from B-Cell clones described as?

A

Monoclonal antibodies.

52
Q

What can the B-Cell clones differentiate into?

A

Plasma cells and memory cells.

53
Q

What do plasma cells do?

A

Primary immune response. They create a specific antibody. It is secreted into blood plasma. Antibodies are created at a rate of 2000+ per second. The cells only last a few days.

54
Q

What do memory cells do?

A

Secondary immune response. They don’t create antibodies. They last a long time in the body, when they encounter the complimentary antigen to their antibody, they are stimulated to divide rapidly. This creates lots of memory and plasma cells quickly, and therefore lots of antibodies are created quickly.

55
Q

Why is the secondary immune response much faster and of a greater magnitude than the primary immune response?

A

The primary response relies on the activation of both the specific TH Cell and B-Cells before antibodies can be released. The secondary immune response needs only the B-Memory Cell to be activated, and there would be more of those in the blood.

56
Q

What are the stages of Humoral immunity?

A

1 - surface antigens of a pathogen are taken in by a specific B-Cell
2 - The B-Cell processes the antigen to place them on its cell surface membrane.
3 - TH Cell attaches to the presented antigens and activates it.
4 - The B-Cell is now activated , it divides by mitosis. The clones differentiate into plasma or memory cells.
5 - Plasma cells secrete a specific antibody to fit the pathogen’s specific antigen.
6 - The antibody attaches and destroys the pathogen.
The memory cells stay in the blood until activated again by the specific antigen. Causing the secondary immune response.

57
Q

What is an antibody?

A

A protein created by a B-Cell, it has two identical, specific, binding sites.

58
Q

What do antibodies do?

A

It binds to a specific antigen, which is complementary to its specific binding site.

59
Q

What are antibodies made of? What is their basic structure?

A

THey are made of 4 polypeptide chains. 2 Long (Heavy chains). 2 short (Light chains.)

60
Q

Draw and label an antibody,

A
61
Q

What is the name given to the binding site of an antibody?

A

The variable region. This is due to it being specific to a particular antibody, so they are all different.

62
Q

What causes the variable region of an antibody to be different?

A

The sequence of amino acids that form a specific 3D shape.

63
Q

What is the part of the antibody that isn’t the variable region called?

A

The constant region

64
Q

Do antibodies destroy pathogens?

A

Not directly, but they aid in their destruction.

65
Q

What do antibodies do to pathogens?

A

1 - Cause agglutination through binding to two pathogens at once. Many pathogens can be clumped together in this way.
2 - They act as markers to stimulate phagocytosis

66
Q

How are monoclonal antibodies used to treat diseases (specifically cancer).

A

Direct monoclonal antibody therapy and indirect monoclonal antibody therapy.

67
Q

How does direct monoclonal antibody therapy work?

A

1 - Monoclonal antibodies are created which will attach to specific antigens on cancer cells
2 - These are given to the patient. They attach only to the cancer cell’s receptors
3 -This blocks the signals required to stimulate uncontrolled mitosis.

68
Q

How does indirect monoclonal antibody therapy work?

A

1 - Monoclonal antibodies are created which will attach to specific antigens on cancer cells
2 - A cytotoxic (cell killing) drug, or radioactive substance is attached to the monoclonal antibody
3 - These are given to the patient. They attach only to the cancer cell’s receptors
4 -This kills the cell.

69
Q

What are the benefits of using monoclonal antibodies in medical diagnosis?

A

They produce results very quickly.

70
Q

How are monoclonal antibodies used in pregnancy testing?

A

1 - Pregnant Women produce HCG Hormone in their Urine.
2 - Test Strip has 3 parts to it
1st: start contains antibodies complementary to HCG,
2nd: middle contains antibodies complementary to HCG-Antibody complex,
3rd: end contains antibodies complementary to HCG Antibodies).
3 - If woman is pregnant, HCG in the urine binds to antibodies on 1st part forming a HCG-Antibody complex,
4 - The HCG-Antibody complex then binds to antibodies on the 2nd part forming a blue line (positive result),
5 - HCG Antibodies also bind to the 3rd part as a control .
6 - If woman is not pregnant, no HCG in urine so nothing binds to HCG Antibodies in 1st part, so nothing binds to antibodies in 2nd part leaving no blue line (negative result),
7 - The HCG Antibodies still bind to 3rd part for the control

71
Q

Why are there ethical issues with creating monoclonal antibodies?

A

Mice are used to create them, this involves giving them cancer.

72
Q

What have been the successes and failures of monoclonal antibodies?

A

They have been very successful in treating cancer and diabetes. They have also been associated with deaths whilst being used to treat multiple sclerosis.

73
Q

What are the two main types of immunity?

A

Passive and active.

74
Q

What are the two types of active immunity?

A

Natural and artificial.

75
Q

What is passive immunity?

A

Antibodies are given to a person. The body isn’t creating them.

76
Q

What are examples of passive immunity?

A

An anti-tetanus injection, breastfeeding.

77
Q

What is active immunity?

A

Where the body responds to antigens. This stimulates the production of antibodies.

78
Q

What is natural active immunity?

A

Where a person is infected with a particular disease. Their body responds as normal and develops immunity.

79
Q

What is artificial active immunity?

A

Where a person is given a vaccination. This causes an immune response to occur.

80
Q

Why do we bother with artificial immunity?

A

The person being vaccinated can develop immunity without suffering the symptoms of the disease. The disease may develop faster than the immune response, and lead to serious illness or death.

81
Q

What does a vaccine contain?

A

One or more types of antigen from the disease causing pathogen.

82
Q

What is the most important result of a vaccination?

A

The creation of memory cells.

83
Q

Why is it important that vaccination creates memory cells?

A

This speeds up and intensifies the immune response for future infections. Antibodies are rapidly produced before the person gets ill.

84
Q

What is a vaccination programme?

A

The delivery of a vaccination to the population.

85
Q

What makes a vaccination programme successful?

A

Economical to produce large volumes
Limited side-effects (to avoid discouraging people for getting vaccinated)
Ability to produce, store and transport the vaccine.
Training of staff for delivery of the vaccination
Vaccination of a high proportion of people to create herd immunity.

86
Q

What is herd immunity?

A

Herd immunity allows those unvaccinated to stay safe from disease as there are enough vaccinated people that the pathogen is very unlikely to be passed on.

87
Q

Why is herd immunity so important?

A

Certain people, such as very young children/babies or ill/immunocompromised people can’t be vaccinated. They need the protection of the other vaccinated people.

88
Q

Why might vaccination not eradicate a disease?

A

The pathogen may mutate so rapidly that vaccines will stop working.
Some people won’t develop immunity (E.g. immunocompromised)
If the disease is caught soon after vaccination, the immune system hasn’t had a chance to develop protection.
There may be multiple variations of the pathogen.
The pathogens may be hidden in the body (inside cells, or areas away from tissue fluid such as intestines)
Some people do not get vaccinated, typically due to misunderstanding of risks. Or religious views.

89
Q

What are the ethical concerns of vaccinations?

A

the use of animals in their production
Side effects
Testing of vaccines and the risk to individuals
Should vaccination be compulsory to create herd immunity?

90
Q

What is the full name of HIV?

A

The Human Immunodeficiency Virus

91
Q

What disease can having HIV lead to?

A

Acquired Immune Deficiency Syndrome (AIDS)

92
Q

What are the component parts of HIV?

A

Lipid envelope, attachment proteins, protein layer called capsid, RNA, enzymes.

93
Q

What group of viruses does HIV belong to?

A

Retroviruses

94
Q

How does HIV replicate (basic)

A

It uses the host cell’s organelles to create the component parts.

95
Q

What are the stages involved in HIV replication?

A

1 - HIV enters the bloodstream
2 - HIV attachment proteins bind to receptor proteins. (Named CD4 found most often on T-Cells)
3 - Protein capsid fuses to the cell membrane
4 - HIV enzymes copy the HIV RNA as DNA
5 - The DNA moves into the nucleus where it fuses with the host cell’s DNA
6 - The Cell’s enzymes create mRNA from the HIV DNA template. This leaves the nucleus through the nuclear pores.
7 - Protein synthesis creates the HIV components
8 - The HIV components break out of the cell, with the cell surface membrane forming the lipid envelope.

96
Q

Why does HIV damage the immune system?

A

The HIV virus’ attachment proteins specifically bind to receptors on T-Helper cells. These therefore can’t stimulate B-Cells or cytotoxic T cells. Memory cells also can’t be formed.

97
Q

How dangerous is HIV alone?

A

HIV itself doesn’t cause much harm. It is the effect of a weakened immune system that is dangerous.

98
Q

Why is HIV indirectly dangerous?

A

As the virus damages the immune system, the individual can’t respond adequately to new pathogens.

99
Q

What is the test used to identify the presence of specific proteins?

A

The ELISA test

100
Q

What does the ELISA test stand for?

A

Enzyme Linked ImmunoSorbent Assay

101
Q

What are the stages of the ELISA test?

A

1 - Sample applied to a slide (attached to it)
2 - Excess removed
3 - Specific antibodies, complimentary to the protein introduced
4 - Excess removed
5 - A second antibody, complimentary to the first introduced. - This has an enzyme attached.
6 - A colourless substrate of the enzyme added. The enzyme acts on the substrate changing its colour.
7 - The intensity of the colour indicates the abundance of the protein tested for.

102
Q

What can the ELISA test be used for?

A

Identifying the presence of pathogens such as HIV. Also drugs or allergen tests, where the quantity of substance is more important than its presence.

103
Q

What is one way in which antibiotics work?

A

By stopping the production of the cell wall of a bacteria.

104
Q

Why is the cell wall of a bacteria so important?

A

It prevents the destruction of the cell by osmotic lysis.

105
Q

What is the cell wall of a bacterium made from?

A

Peptidoglycan (Meurin)

106
Q

How would the inhibition of enzymes building the cell wall cause the bacterium to die?

A

If the cell wall isn’t as strong, it won’t withstand the outward forces caused through the movement of water by osmosis. The influx of water can cause the cell to break apart.

107
Q

What are the different reasons by which antibiotics can not affect viruses?

A

1 - They do not carry out metabolic processes, so these can not be stopped.
2 - They do not have a peptidoglycan (murein) wall.
3 - They are hidden within the host’s cells.

A-level Biology Longridge Towers School (37 decks)

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